What is the difference between horizontal and vertical pod autoscaling?

Question

Accepted Answer

**Horizontal** — add more pods. **Vertical** — resize pods.

**Horizontal Pod Autoscaling (HPA):**
- Add/remove pods.
- Based on CPU/memory.
- Most common.
- Scales out.

```
HPA:
CPU > 70% → Add pod
CPU < 30% → Remove pod
[Pod] [Pod] [Pod] → [Pod] [Pod] [Pod] [Pod]
(More pods)
```

**Vertical Pod Autoscaling (VPA):**
- Resize existing pods.
- Increase CPU/memory.
- Requires restart.
- Scales up.

```
VPA:
[Pod: 256MB] → [Pod: 512MB]
(Bigger pod)
```

**Key differences:**
- **Horizontal** — more pods.
- **Vertical** — bigger pods.
- **Horizontal** — no restart.
- **Vertical** — restart needed.

Systems Analyst: What is the difference between horizontal and vertical pod autoscaling?